Correctly setup tooltip's style as theme variation

scene/theme/default_theme.cpp

@@ -1025,9 +1025,11 @@ void fill_default_theme(Ref<Theme> &theme, const Ref<Font> &default_font, const
 
 	// TooltipPanel + TooltipLabel
 
+	theme->set_type_variation("TooltipPanel", "PopupPanel");
 	theme->set_stylebox("panel", "TooltipPanel",
 			make_flat_stylebox(Color(0, 0, 0, 0.5), 2 * default_margin, 0.5 * default_margin, 2 * default_margin, 0.5 * default_margin));
 
+	theme->set_type_variation("TooltipLabel", "Label");
 	theme->set_font_size("font_size", "TooltipLabel", -1);
 	theme->set_font("font", "TooltipLabel", Ref<Font>());